<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot>
      </slot>
    </div>
    <div class="dots">
      <span class="dot" v-for="(item,index) in dots" :class="{
        active:currentPageIndex===index
        }" :key="index">

      </span>
    </div>
  </div>
</template>

<script type="text/ecmascript-6">
import BScroll from 'better-scroll'
import {addClass} from 'common/js/dom'
export default {
  data() {
    return {
      dots: [],
      currentPageIndex: 0
    }
  },
  props: {
    loop: {
      type: Boolean,
      default: true
    },
    autoPlay: {
      type: Boolean,
      default: true
    },
    interval: {
      type: Number,
      default: 4000
    }
  },
  mounted() {
    // 浏览器刷新时间一般是17
    setTimeout(() => {
      this._setSliderWidth()
      this._initDots()
      this._initSlider()
      if (this.autoPlay) {
        this._play()
      }
    }, 20)
    window.addEventListener('resize', () => {
      if (!this.slider) {
        return
      }
      this._setSliderWidth(true)
      this.slider.refresh()
    })
  },
  methods: {
    _setSliderWidth(isResize) {
      this.children = this.$refs.sliderGroup.children
      let width = 0
      let sliderWidth = this.$refs.slider.clientWidth
      for (let i = 0; i < this.children.length; i++) {
        let child = this.children[i]
        addClass(child, 'slider-item')
        child.style.width = sliderWidth + 'px'
        width += sliderWidth
      }
      if (this.loop && !isResize) {
        width += 2 * sliderWidth
      }

      this.$refs.sliderGroup.style.width = width + 'px'
    },
    _initDots() {
      this.dots = new Array(this.children.length)
    },
    _play() {
      let pageIndex = this.currentPageIndex + 1
      if (this.loop) {
        pageIndex += 1
      }
      this.timer = setTimeout(() => {
        this.slider.goToPage(pageIndex, 0, 400)
      }, this.interval)
    },
    _initSlider() {
      this.slider = new BScroll(this.$refs.slider, {
        scrollX: true,
        scrollY: false,
        momentum: false,
        snap: true,
        snapLoop: this.loop,
        snapThreshold: 0.3,
        snapSpeed: 400
      })

      this.slider.on('scrollEnd', () => {
        let pageIndex = this.slider.getCurrentPage().pageX
        if (this.loop) {
          pageIndex -= 1
          this.currentPageIndex = pageIndex
          if (this.autoPlay) {
            clearTimeout(this.timer)
            this._play()
          }
        }
      })
    }
  },
  destroyed() {
    clearTimeout(this.timer)
  }
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
@import "~common/stylus/variable"
 .slider
   min-height: 1px
   .slider-group
     position: relative
     overflow: hidden
     white-space: nowrap
     .slider-item
       float: left
       box-sizing: border-box
       overflow: hidden
       text-align: center
       a
         display: block
         width: 100%
         overflow: hidden
         text-decoration: none
       img
         display: block
         width: 100%
   .dots
     position: absolute
     right: 0
     left: 0
     bottom: 12px
     transform: translateZ(1px)
     text-align: center
     font-size: 0
     .dot
       display: inline-block
       margin: 0 4px
       width: 8px
       height: 8px
       border-radius: 50%
       background: $color-text-l
       &.active
         width: 20px
         border-radius: 5px
         background: $color-text-ll
</style>
